23 Asymmetric Catalysis and Chromatographic …
487
Fig. 23.3 X-ray structure of (R)-MOF-9
23.2.8 Friedel–Crafts Alkylation
In 2012, Lin and co-workers [16] constructed novel chiral (R)-MOF-11 with Brønsted acid sites from (R)-1,1’-binaphthyl-2,2’-phosphoric acid derivative 11 and
Cu(NO 3 ) 2 . (R)-MOF-11 was found to be an active catalyst for the Friedel–Crafts
reaction between indoles and N-sulfonyl aldimines. The reaction preferentially
formed the corresponding R isomer (Table 23.11). Interestingly, methyl ester ligand
11 predominantly formed the S isomer.
In 2018, Tanaka and co-workers [18] reported the first highly enantioselective Friedel–Crafts alkylation of N,N-dialkylanilines with trans-β-nitrostyrene
catalyzed by homochiral (R)-MOF-12 [17] constructed from (R)-2,2’-dihydroxy1,1’-binaphthyl-6,6’-dicarboxylic acid 12 (Fig. 23.4). The Friedel–Crafts reaction
was explored with a range of N,N-dialkylanilines, which successfully reacted with
trans-β-nitrostyrene in the presence of 20 mol% of the evacuated MOF, affording the
corresponding products in excellent yields (~96%) and enantioselectivities (~98%
ee) (Table 23.12). Sterically more bulky N,N-dibenzylaniline showed poor catalytic
efficiency in terms of both the product yield (5%) and enantioselectivity (26% ee).
This may be because of the weaker encapsulation of the sterically bulky reactant
in the chiral cavities of (R)-MOF-12. The catalyst was separated by filtration and
successfully used for two further catalytic cycles without loss of catalytic activity.
On the basis of the above results, the reaction was extended to pyrrole and N-methyl
pyrrole, and it was found that (R)-MOF-12 can also efficiently catalyzed the reaction
487
Fig. 23.3 X-ray structure of (R)-MOF-9
23.2.8 Friedel–Crafts Alkylation
In 2012, Lin and co-workers [16] constructed novel chiral (R)-MOF-11 with Brønsted acid sites from (R)-1,1’-binaphthyl-2,2’-phosphoric acid derivative 11 and
Cu(NO 3 ) 2 . (R)-MOF-11 was found to be an active catalyst for the Friedel–Crafts
reaction between indoles and N-sulfonyl aldimines. The reaction preferentially
formed the corresponding R isomer (Table 23.11). Interestingly, methyl ester ligand
11 predominantly formed the S isomer.
In 2018, Tanaka and co-workers [18] reported the first highly enantioselective Friedel–Crafts alkylation of N,N-dialkylanilines with trans-β-nitrostyrene
catalyzed by homochiral (R)-MOF-12 [17] constructed from (R)-2,2’-dihydroxy1,1’-binaphthyl-6,6’-dicarboxylic acid 12 (Fig. 23.4). The Friedel–Crafts reaction
was explored with a range of N,N-dialkylanilines, which successfully reacted with
trans-β-nitrostyrene in the presence of 20 mol% of the evacuated MOF, affording the
corresponding products in excellent yields (~96%) and enantioselectivities (~98%
ee) (Table 23.12). Sterically more bulky N,N-dibenzylaniline showed poor catalytic
efficiency in terms of both the product yield (5%) and enantioselectivity (26% ee).
This may be because of the weaker encapsulation of the sterically bulky reactant
in the chiral cavities of (R)-MOF-12. The catalyst was separated by filtration and
successfully used for two further catalytic cycles without loss of catalytic activity.
On the basis of the above results, the reaction was extended to pyrrole and N-methyl
pyrrole, and it was found that (R)-MOF-12 can also efficiently catalyzed the reaction